A capital asset is defined to include property of any kind held by an assessee, whether connected with their business or profession or not connected with their business or profession. It includes all kinds of property, movable or immovable, tangible or intangible, fixed or circulating. Thus, land and building, plant and machinery, motorcar, furniture, jewellery, route permits, goodwill, tenancy rights, patents, trademarks, shares, debentures, securities, units, mutual funds, zero-coupon bonds etc. are capital assets.
However this advice is questionable beyond the US private context. Several public sector standards in global use, notably triple bottom line accounting as defined by ICLEI for world cities, require that employees or the environment or something else be treated as a capital asset. In this context it means something managers have a responsibility to maintain, and to report changes in value as gains or losses. See human capital, natural capital, triple bottom line, human development theory.
Capital assets should not be confused with the capital a financial institution is required to hold. This capital is computed from the right-hand side of the balance sheet while assets are found on the left-hand side. See Basel III for a summary of how such requirements are proposed to be calculated.